Reply #5: I once had a yard that had an entire hedge of very old lilacs

[rosesaylavee]

At the time I was subscribed to Horticulture magazine and they luckily had an article about pruning lilacs. Best time to prune is spring of course but this fall would do fine as well. I pruned mine back as recommended in the article - down to the point where the bush was about a foot to two feet tall. Took out all the old growth and then prayed I hadn't killed the poor things. The next spring they were still alive and we only had leaves no flowers. I think by the following year, there were flowers again and the height was about 4 feet tall. It takes a while to see the flowers come back but getting the old stuff out of there and allowing new growth to happen is key. Good luck!